Sten Petersen

Bone mineralisation in premature infants cannot be predicted from serum alkaline phosphatase or serum phosphate

Background: The bone mineral content of premature infants at term is lower than in mature infants at the same postconceptional age. Serum alkaline phosphatase and serum phosphate are often used as indicators of bone mineralisation. Objective: To analyse the association between bone mineral content and serum alkaline phosphatase and serum phosphate. Methods: Serum alkaline phosphatase and phosphate were measured at weekly intervals during admission in 108 premature infants of gestational age below 32 weeks (mean (SD) gestational age 29 (2) weeks; mean (SD) birth weight 1129 (279) g). Bone mineral content was measured at term (mean gestational age 41 weeks) by dual energy x ray absorptiometry and corrected for body size. Results: Serum alkaline phosphatase was significantly negatively associated with serum phosphate (p < 0.001). Bone mineral content was not associated with mean serum alkaline phosphatase (p = 0.8), peak serum alkaline phosphatase (p = 0.5), or mean serum phosphate (p = 0.2) at term. Conclusion: Routine measurements of serum alkaline phosphatase and serum phosphate are of no use in predicting bone mineralisation outcome in premature infants.

Diet and Bone Mineral Content at Term in Premature Infants

Premature infants are at risk of developing metabolic bone disease mainly because of low calcium and phosphorus intake. We have examined the effect of different mineral supplements on bone mineral content at term in 127 premature infants with gestational age <32 wk in a double-blinded randomized trial. We used either phosphate supplementation of human milk as recommended by the European Society of Pediatric Gastroenterology and Nutrition or fortified supplementation with protein, calcium, and phosphorus or preterm formula as recommended by the American Academy of Pediatrics. The intervention period was from 1 week old until 36 wk of gestational age, and the infants were fed approximately 200 mL·kg−1·d−1. Bone mineral content was measured at term by dual-energy x-ray absorptiometry scan. Surprisingly, neither phosphate, fortifier, nor preterm formula supplementation had any significant effect on bone mineral content at term compared with infants fed their own mothers milk only. There was a tendency to higher total bone mineral content in infants fed preterm formula compared with infants fed their own mothers milk only (p = 0.05), but when the bone mineral content was corrected for the size of the infant, there was no difference (p = 0.68). Infants fed preterm formula had a significantly higher weight at term compared with infants fed their own mothers milk only (p = 0.02), but did not differ significantly in length or head circumference. In a regression analysis, the amount of supplemented phosphorus was significantly associated with weight at term (p = 0.008). We conclude that when feeding 200 mL·kg−1·d−1, mineral supplementation of human milk or use of preterm formula does not significantly improve bone mineralization outcome at term.

Macronutrients in Milk from Mothers Delivering Preterm

UNLABELLED Premature infants require large amounts of protein and energy to achieve normal growth. Feeding with human milk alone is therefore only regarded acceptable if the protein and energy content is adequate. METHODS 476 milk samples from 101 mothers delivering before the 32nd gestational week (mean gestational age, 28 weeks) were obtained on a weekly basis until 36 weeks of gestational age and analyzed for true protein, total carbohydrate, and fat content by infrared analysis. Fat measurements were validated with the Folch method. Milk was collected by complete expression with an electric pump into 24-hour pools. RESULTS The protein concentration decreased significantly with time (P = 0.00001). The carbohydrate, fat, and energy concentration was significantly lower in the first 2 weeks after delivery, after which they increased to a constant level. The macronutrient level in milk was not associated with gestational age (P = 0.3). The energy content of these milk samples was high, and feeding 200 mL/kg would provide sufficient energy until 36 weeks of gestational age for all infants, and 65% of the infants would receive > or =3g total protein/kg/day.

Diet, Growth, and Bone Mineralization in Premature Infants

Energy, protein, and mineral requirements in premature infants are high, hence increasing the risk of poor growth and development of metabolic bone disease. This double-blind study included 127 consecutive premature infants with gestational age below 32 weeks. Both sick and healthy infants participated. Average duration of ventilator treatment: 2 days, CPAP treatment: 10 days (range, 0-50d). Infants were randomized to 3 groups from 1 week old to 37 weeks of gestational age and fed the following: a) human milk (their own mothers milk or banked milk) supplemented with phosphate, b) human milk fortified with protein, calcium, and phosphate, or c) unsupplemented mothers milk or preterm formula. Infants randomized to preterm formula were fed formula only if their own mothers milk was not available, hence there were 2 subgroups of infants fed either unsupplemented human milk or preterm formula. Volume of intake was 191+/-14mL/kg/d (mean +/- SD); linear growth was measured weekly by knemometry; head circumference was measured weekly; and growth rate was calculated by linear regression for each infant. Bone mineralization and body composition were measured by DEXA-scan (Hologic 1000/W) at term. There was a tendency toward slower growth and less bone mineral content in infants fed unsupplemented human milk but, surprisingly, the difference was small and not significant.